This manual was developed in response to teachers' requests for help in maintaining focus and resolving questions and concerns arising out of the Questioning and Understanding to Improve Learning and Thinking (QUILT) program. The introduction describes collegial investigation as a structural process that groups can use to examine problems, issues, or proposals. Two major concepts--the postulate and the collegium--are fundamental to the design of the collegial investigation, and two distinct scaffoldings--critical thinking and action research--guide its functioning. Success depends on three norms: collegiality, practical inquiry, and knowledge. The collegial investigation uses a framework for action research that deploys members in one of five investigating teams: (1) philosophers who read and reflect upon selected pieces from journals and books; (2) analysts who identify and analyze data sources; (3) surveyors who formulate questions which they pose to selected audiences via survey forms or interviews; (4) people watchers who observe individuals and groups in specified contexts; and (5) storytellers who solicit stories from their colleagues and reflect on their own experiences. Sections of the paper explore patterns for critical thinking and the roles and responsibilities of the investigating teams. Also included are forms for investigators' notes and pages for journal keeping. (ND)